1. Field of the Invention
This invention concerns apparatus for aiding the maintenance and repair of engines, such as diesel engines; the subject apparatus being employed for pulling the piston out from its associated cylinder.
2. Background and Prior Art
The repair and/or maintenance of reciprocating engines, having pistons or piston rods moving back and forth linearly within cylinders, often requires the removal of a piston from within its respective cylinder. The removal of a piston usually presents minimal effort/problem with respect to small engines, having small diameter cylinders and associated pistons, as with passenger automobiles. However, larger reciprocating engines, especially diesel engines, can present a difficult task in the removal of a piston, without damage to the piston, its cylinder and adjacent components. A common method for removing pistons has been to drive them out manually, as with a mallet, from one end of the cylinder, out through the opposite end. Such manual/mallet method often is physically difficult, too time consuming, and can damage the piston, cylinder, cylinder liner, bearings, crank shaft, connecting rod, piston cooler nozzle, etc. Some very large diesel engines, such as for railroad and ocean liners, construct the top of the piston to receive a large eye bolt or chain, which is attached to the piston at the time for its removal. At such removal time, a pulling mechanism, such as a block and tackle, is connected to the eyebolt; and the piston is pulled from the cylinder. One problem with this pulling approach is the need for supporting the upper end of the block and tackle. Another problem is that the top surface of the piston has to be threaded to receive the eyebolt. It is neither practical nor time effective to thread the top surface at time of pulling. Also, the piston body could be weakened if the piston diameter and length are relatively small, as with diesel engines, for various classes and types of marine, automotive, truck and stationary engine applications.
As well known, a piston slides tightly within the cylinder liner, its cylinder or engine block. Usually, the top of a piston of a diesel engine is formed with a combustion or compression bowl, having a generally vertical interior side. Often, the bowl has a base diameter smaller or larger than the diameter at its upper top lip; thus, not providing any good clamping surfaces for a tool pulling the piston from the cylinder liner, engine block and/or cylinder.
The prior art does teach a piston puller to L. Gregg U.S. Pat. No. 4,019,235 useable after the cylinder liner is removed. Thereupon, a sleeve of the tool is inserted in the annular space vacated by the liner and has a bottom end which surrounds the exterior bottom of the piston. The tool then is pulled upward to remove its sleeve and the piston it is grasping. Another piston puller uses a turnbuckle for pulling a piston from a cylinder. The turnbuckle is placed into the combustion bowl, with the turnbuckle""s two ends pointed towards opposite interior sides of the bowl. Then, a short rod is placed manually into the center of the turnbuckle, or a small wrench clamps over it, and is pivoted through a plurality of small accurate motions, with the rod or wrench moved away from the longitudinal axis of the piston, to tighten the turnbuckle ends into the combustion bowl. The turnbuckle continues to lie at right angle to the longitudinal axis of the piston. Next, the turnbuckle is pulled vertically along the longitudinal axis of the piston, to pull the piston from the cylinder liner. This turnbuckle apparatus and method is slow, inconvenient, if not impossible, to use. For example, some compression bowls, such as for the Caterpillar and Cummins 5xc2xdxe2x80x3 and 5xe2x85x9c bores, have an upward projectionxe2x80x94cone shapedxe2x80x94in the center of the bowl. Hence, a turnbuckle-like device could not lie across the interior diameter of the bowl. At best, it is difficult to provide sufficient grip upon the interior side of the combustion bowl; whereupon, the apparatus can slip out of the bowl, damaging the bowl, the cylinder liner, etc. and the hand of the user.
The present invention is an apparatus easy to use manually, applies a significantly sufficient force quickly upon the entire interior side surface of the combustion bowl, and is safe to use. This apparatus has a radially expanding mandrel comprised of a plurality of gripping segments. The radially exterior surfaces of these segments are arcuate and are wedged or cammed outwardly against the entire interior surface of the circular sidewall of the combustion bowl by the axial lifting of a wedge shaped base member against the interior surface of the mating mandrel segments. The lifting of the wedge shaped base member is achieved by the manual rotation of a threaded shaft, which is coaxial with the expanding mandrel and the piston. The mechanical force ratio of the invention is significant, such that turning of the threaded shaft, as by a handle, is done easily and quickly, with high mechanical leverage/force and a resulting very positive fit of the mandrel segments against the inside of the combustion bowl.